The microsolvated complexes of formanilide, generated in a supersonic expansion, have been observed by Fourier transform microwave spectroscopy. Three 1 : 1 and one 1 : 2 formanilide-water adducts ...have been observed and their structures characterized by the measurement of isotopologue rotational spectra. In one of the monohydrated complexes and in the dihydrated complex, formanilide adopts a cis-configuration. In these species water closes sequential cycles with the cis amino and carbonyl groups through a network of N-HO and O-HO hydrogen bonds. Furthermore, in these complexes cis-formanilide has almost the same non planar configuration observed in the monomer. In the two monohydrated complexes detected with trans-formanilide, a planar skeleton is detected with water interacting solely with either the amino (N-H··O bond) or the carbonyl group (O-HOdouble bond, length as m-dashC bond). The observed tunnelling splittings show a rich intermolecular dynamics in those complexes. The results seem to indicate that complexation with water switches the configuration of formanilide from trans, which is more stable for the bare monomer, to cis, which is more stable for the hydrated complexes.
Diadamantyl ether (DAE, C20H30O) represents a good model to study the interplay between London dispersion and hydrogen‐bond interactions. By using broadband rotational spectroscopy, an accurate ...experimental structure of the diadamantyl ether monomer is obtained and its aggregates with water and a variety of aliphatic alcohols of increasing size are analyzed. In the monomer, C−H⋅⋅⋅H−C London dispersion attractions between the two adamantyl subunits further stabilize its structure. Water and the alcohol partners bind to diadamantyl ether through hydrogen bonding and non‐covalent Owater/alcohol⋅⋅⋅H−CDAE and C−Halcohol⋅⋅⋅H−CDAE interactions. Electrostatic contributions drive the stabilization of all the complexes, whereas London dispersion interactions become more pronounced with increasing size of the alcohol. Complexes with dominant dispersion contributions are significantly higher in energy and were not observed in the experiment. The results presented herein shed light on the first steps of microsolvation and aggregation of molecular complexes with London dispersion energy donor (DED) groups and the kind of interactions that control them.
Alkyl groups matter: Complexes between diadamantyl ether (DAE) and water and alcohols with increasing side‐chain size have been studied by using rotational spectroscopy. DAE and the clustering molecules interact through an O−H⋅⋅⋅O hydrogen bond and London dispersion (LD) interactions. The H−C⋅⋅⋅H−C LD attractions take place between the alkyl groups of the alcohols and those of DAE. The LD interactions increase with increasing size of the alcohol.
We performed a comprehensive investigation of methyl cyanoacetate (MCA) using high-resolution Fourier transform rotational spectroscopy. Two low energy conformers of MCA were observed in the ...vibrational ground state, in selected frequency regions from 2 to 110 GHz. We report accurately determined line lists, rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants for both conformers, as well as for several singly substituted heavy-atom isotopologues. One of the conformers was previously reported; however, the rotational transitions of the second conformer, which is newly described here, are observed to be generally more intense than the latter. The accurate predictions of rotational transitions into the millimeter-wave region can facilitate the detection of these conformers of MCA in the interstellar medium. Using the rotational spectroscopy data provided here, we searched for the two conformers of MCA in a deep and unbiased spectral survey of the molecular cloud G+0.693-0.027 located in the Galactic Center. None of the MCA conformers were detected. The upper limits for their abundances were derived with respect to the abundance of molecular hydrogen.
The initial stages of the gas‐phase nucleation between CO2 and monoethanolamine were investigated via broadband rotational spectroscopy with the aid of extensive theoretical structure sampling. ...Sub‐nanometer‐scale aggregation patterns of monoethanolamine‐(CO2)n, n=1–4, were identified. An interesting competition between the monoethanolamine intramolecular hydrogen bond and the intermolecular interactions between monoethanolamine and CO2 upon cluster growth was discovered, revealing an intriguing CO2 binding priority to the hydroxyl group over the amine group. These findings are in sharp contrast to the general results for aqueous solutions. In the quinary complex, a cap‐like CO2 tetramer was observed cooperatively surrounding the monoethanolamine. As the cluster approaches the critical size of new particle formation, the contribution of CO2 self‐assembly to the overall stability increases.
How does CO2 interact with an alkanolamine in the gas phase? Using rotational spectroscopy, non‐reactive complexes monoethanolamine‐(CO2)n (where n=1–4) were characterized. It was discovered that CO2 has a binding priority to the hydroxyl group over the amine group. This is in sharp contrast to the general results observed in the solution phase.
The initial stages of the gas-phase nucleation between CO
and monoethanolamine were investigated via broadband rotational spectroscopy with the aid of extensive theoretical structure sampling. ...Sub-nanometer-scale aggregation patterns of monoethanolamine-(CO
)
, n=1-4, were identified. An interesting competition between the monoethanolamine intramolecular hydrogen bond and the intermolecular interactions between monoethanolamine and CO
upon cluster growth was discovered, revealing an intriguing CO
binding priority to the hydroxyl group over the amine group. These findings are in sharp contrast to the general results for aqueous solutions. In the quinary complex, a cap-like CO
tetramer was observed cooperatively surrounding the monoethanolamine. As the cluster approaches the critical size of new particle formation, the contribution of CO
self-assembly to the overall stability increases.
The Cover Feature illustrates similarities and differences between oxygen and sulfur when being part of bulky molecules, as detected by high‐resolution rotational spectroscopy. While the change from ...oxygen to sulfur does not affect much the structure of the compounds, their microhydrated complexes highlight a difference in hydrogen bond formation capabilities. More information can be found in the Research Article by Pablo Pinacho, Marina Šekutor, Melanie Schnell, and co‐workers.
Water self-association dominates the formation of microsolvated molecular clusters which may give rise to complex structures resembling those of pure water clusters. We present a rotational study of ...the complex formamide–(H2O)3 formed in a supersonic jet and several monosubstituted isotopologues. Formamide and water molecules form a four-body sequential cycle through N–H···O, O–H···O, and O–H···OC hydrogen bonds, resulting in a chiral structure with a nonplanar skeleton that can be overlapped to that of water pentamer. The analysis of the 14N-nucleus quadrupole coupling effects shows the depletion of the electron density of the N atom lone pair with respect to the bare formamide that affects the amide group C–N and CO distances. The study of the observed tunneling doublets shows that formamide–(H2O)3 follows a path to invert its structure driven by the flipping of water subunits and passing through successive nonplanar configurations, a motion reminiscent of the pseudorotation of water pentamer.
The structure of isolated 1‐chloronaphthalene has been investigated in a supersonic expansion by high‐resolution chirped‐pulse Fourier transform microwave (CP‐FTMW) spectroscopy in the 2–8 GHz ...frequency range. Accurate values of the rotational, centrifugal distortion, and nuclear quadrupole coupling constants for the only availabe conformer have been determined. The intensity of the spectrum allowed us to observe all the heavy atoms isotopologues in natural abundance, determining their rotational constants. From the extensive experimental dataset we derived accurate structures for 1‐chloronaphthalene using different methodologies and compared with related compounds.
A detailed study of the spectrum of 1‐Chloronaphthalene, recorded using rotational spectroscopy, is presented. The high sensitivity of the chirped pulse FTMW instrument allows the detection of all the heavy‐atom isotopologues needed for the accurate determination of the experimental structure.
The microsolvated complexes of formanilide, generated in a supersonic expansion, have been observed by Fourier transform microwave spectroscopy. Three 1 : 1 and one 1 : 2 formanilide-water adducts ...have been observed and their structures characterized by the measurement of isotopologue rotational spectra. In one of the monohydrated complexes and in the dihydrated complex, formanilide adopts a
cis
-configuration. In these species water closes sequential cycles with the
cis
amino and carbonyl groups through a network of N-H O and O-H O hydrogen bonds. Furthermore, in these complexes
cis
-formanilide has almost the same non planar configuration observed in the monomer. In the two monohydrated complexes detected with
trans
-formanilide, a planar skeleton is detected with water interacting solely with either the amino (N-H··O bond) or the carbonyl group (O-H O&z.dbd;C bond). The observed tunnelling splittings show a rich intermolecular dynamics in those complexes. The results seem to indicate that complexation with water switches the configuration of formanilide from
trans
, which is more stable for the bare monomer, to
cis
, which is more stable for the hydrated complexes.
Different interactions of water and formanilide were observed. Water reverts the stability of the
cis
-
trans
formanilide conformational equilibrium.
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